Studies have shown that ancient igneous rocks can support life despite having little energy from rock-water interactions. As these ecosystems change very slowly and the microbes grow very slowly, these stable rocks can keep microbes alive for millions of years.
A new study reports the discovery of microbes pockets living within a sealed fracture in a 2-billion-year-old rock. The rock was excavated from the Bushveld Igneous Complex in South Africa, known for its valuable minerals. It is the oldest find of living microbes in ancient rock.
The research team improved their methods using three imaging techniques: infrared spectroscopy, electron microscopy, and fluorescent microscopy. Using these methods, scientists confirmed the microbes were original to the rock and not contaminated. Studying these microbes could help us learn about early life on Earth and aid in the search for life in ancient Martian rocks.
Yohey Suzuki, lead author and associate professor from the Graduate School of Science at the University of Tokyo, said, “We didn’t know if 2-billion-year-old rocks were habitable. Until now, the oldest geological layer in which living microorganisms had been found was a 100-million-year-old deposit beneath the ocean floor, so this is a fascinating discovery. By studying the DNA and genomes of microbes like these, we may be able to understand the evolution of very early life on Earth.”
The rock sample came from the Bushveld Igneous Complex (BIC) in northeastern South Africa, formed by slowly cooled magma beneath the Earth’s surface. The BIC spans about 66,000 square kilometers and varies in thickness by up to 9 km, holding around 70% of the world’s platinum deposits. Because it has remained stable since its formation with little change, the BIC likely offered a reliable habitat for ancient microbial life to survive until now.
With support from the International Continental Scientific Drilling Program, the team obtained a 30-centimeter rock core sample from about 15 meters underground. They sliced the rock for analysis and found living microbial cells densely packed in cracks. The cracks were sealed with clay, preventing other organisms from entering or leaving.
The team used a previously developed method to ensure the microbes were native to the rock and not contaminated. By staining the microbial DNA and using infrared spectroscopy to analyze the proteins, they confirmed that the microorganisms were alive and not contaminated.
Suzuki said, “I am very interested in the existence of subsurface microbes not only on Earth but also the potential to find them on other planets. NASA’s Mars rover Perseverance is currently due to bring back rocks that are a similar age to those we used in this study. Finding microbial life in samples from Earth from 2 billion years ago and accurately confirming their authenticity makes me excited for what we might be able to now find in samples from Mars.”
Journal Reference:
- Yohey Suzuki, Susan J. Webb, Mariko Kouduka, Hanae Kobayashi, Julio Castillo, Jens Kallmeyer, Kgabo Moganedi, Amy J. Allwright, Reiner Klemd, Frederick Roelofse, Mabatho Mapiloko, Stuart J. Hill, Lewis D. Ashwal, Robert B. Trumbull, “Subsurface Microbial Colonization at Mineral‐Filled Veins in 2‐Billion‐Year‐Old Mafic Rock from the Bushveld Igneous Complex, South Africa,” Microbial Ecology: October 2, 2024, DOI: 10.1007/s00248-024-02434-8.